WDPN31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON 19W (VONGFONG), LOCATED APPROXIMATELY 498 NM NORTH-
NORTHWEST OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 13 KNOTS OVER
THE PAST SIX HOURS. THE CURRENT POSITION ESTIMATE IS BASED, WITH
HIGH CONFIDENCE, ON A RECENT PGTW SATELLITE EYE FIX AND A 070518Z
SSMI IMAGE. THE CURRENT INTENSITY OF 120 KNOTS IS CONSISTENT WITH
DVORAK T-NUMBER ESTIMATES RANGING FROM 5.5 TO 6.5 AND WITH RECENT
AUTOMATED DVORAK INTENSITY ESTIMATES. TY 19W HAS CONTINUED TO
RAPIDLY INTENSIFY OVER THE PAST SIX HOURS, EVIDENCED BY SYMMETRIC
BANDING AND A 27 NM DIAMETER EYE EVIDENT IN RECENT SATELLITE
IMAGERY. UPPER-LEVEL ANALYSIS INDICATES LOW VERTICAL WIND SHEAR AND
MULTIPLE OUTFLOW MECHANISMS, INCLUDING A TROPICAL UPPER-TROPOSPHERIC
TROUGH (TUTT) CELL POSITIONED TO THE EAST. TY 19W CONTINUES TRACKING
GENERALLY WESTWARD ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL STEERING RIDGE.
3. FORECAST REASONING.
A. NEAR-TERM FORECAST INTENSITIES HAVE INCREASED GIVEN THE RECENT
RAPID INTENSIFICATION TREND AND THE TAU 120 FORECAST POSITION HAS
BEEN ADJUSTED SLIGHTLY WESTWARD FROM THE PREVIOUS FORECAST.
HOWEVER, THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TY 19W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE CURRENT STEERING RIDGE THROUGH TAU 36.
THEREAFTER, A MID-LATITUDE TROUGH PASSING TO THE NORTH IS EXPECTED
TO WEAKEN THE STEERING RIDGE, CAUSING THE CYCLONE TO MAKE A SHARP
POLEWARD TURN. THE CYCLONE SHOULD CONTINUE TRACKING GENERALLY
POLEWARD ALONG THE STEERING RIDGE PERIPHERY FROM TAU 36 THROUGH TAU
72. THE DYNAMIC CONSENSUS MODEL GUIDANCE IS IN GENERALLY GOOD
AGREEMENT THROUGH TAU 72, LENDING HIGH CONFIDENCE TO THIS PORTION OF
THE FORECAST TRACK. FAVORABLE UPPER-LEVEL CONDITIONS AND PASSAGE
OVER VERY WARM WATER SHOULD ALLOW THE SYSTEM TO REACH PEAK INTENSITY
DURING THIS PERIOD.
C. TY 19W WILL CONTINUE POLEWARD ALONG THE WESTERN EDGE OF THE
STEERING RIDGE DURING THE EXTENDED FORECAST PERIOD. A TRANSIENT
RIDGE IS EXPECTED TO BUILD TO THE NORTH OF THE SYSTEM LATE IN THE
FORECAST PERIOD, INDUCING A SLIGHT WESTWARD TRACK DEFLECTION BETWEEN
TAU 96 AND TAU 120. DYNAMIC MODEL GUIDANCE SUPPORTS THIS FORECAST
SCENARIO, BUT DEPICTIONS OF THE WESTWARD TRACK DEVIATION VARY.
GIVEN THIS UNCERTAINTY, THE CURRENT EXTENDED FORECAST TRACK LIES IN
THE MIDDLE OF THE FORECAST GUIDANCE NEAR THE MULTI-MODEL CONSENSUS.
TY 19W IS EXPECTED TO WEAKEN SLIGHTLY IN THE EXTENDED PERIOD AS
UPPER-LEVEL OUTFLOW BECOMES LESS FAVORABLE AND ALONG-TRACK OCEAN
HEAT CONTENT DROPS OFF.//
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WDPN31 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W (VONGFONG) WARNING
NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUPER TYPHOON (STY) 19W (VONGFONG), LOCATED APPROXIMATELY 612 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED WEST-
NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY (EIR) REVEALS STY 19W HAS CONTINUED TO
INTENSIFY WITH AN INTENSE RING OF SYMMETRIC CONVECTION SURROUNDING A
DEFINED 17 NM EYE AND MULTIPLE CONVECTIVE BANDS IN THE OUTER
PERIPHERIES FEEDING IN THE SYSTEM. A 071751Z SSMI IMAGE ALSO DEPICTS
AN INTENSE, CONSOLIDATED STRUCTURE WITH IMPROVED BANDING FEATURES,
SPECIFICALLY IN THE NORTHEAST AND SOUTHWEST QUADRANTS. THERE IS HIGH
CONFIDENCE IN THE INITIAL POSITION BASED ON THE DEFINED EYE FEATURE
IN THE EIR LOOP. THE INITIAL INTENSITY HAS INCREASED TO 155 KNOTS
BASED ON DVORAK INTENSITY ESTIMATES FROM PGTW AND RJTD THAT HAVE
INCREASED TO T7.5 (155 KNOTS) AND THE IMPROVED STRUCTURE OBSERVED IN
THE AFOREMENTIONED SATELLITE IMAGERY. UPPER-LEVEL ANALYSIS INDICATES
LOW VERTICAL WIND SHEAR (VWS) AND STRONG POLEWARD AND EQUATORWARD
OUTFLOW CHANNELS WHILE ADDITIONAL VENTING IS BEING INDUCED BY A TUTT
CELL POSITIONED TO THE EAST. STY 19W IS TRACKING GENERALLY WESTWARD
ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE
POSITIONED TO THE NORTHEAST AND HAS NOTICEABLY SLOWED OVER THE PAST
12 HOURS, INDICATIVE OF A WEAKENING STR.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. STY 19W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE WEAKENING STEERING RIDGE THROUGH TAU 12.
AFTER TAU 12, A MID-LATITUDE TROUGH PASSING TO THE NORTH IS EXPECTED
TO BREAK THE STEERING RIDGE, CAUSING THE SYSTEM TO MAKE A SHARP
POLEWARD TURN. STY 19W WILL THEN TRACK GENERALLY POLEWARD ALONG THE
WESTERN PERIPHERY OF THE STEERING RIDGE FROM TAU 24 THROUGH TAU 72.
CONTINUED FAVORABLE UPPER-LEVEL CONDITIONS AND PASSAGE OVER VERY
WARM SEA SURFACE TEMPERATURES SHOULD ALLOW THE SYSTEM TO REACH PEAK
INTENSITY OVER THE NEXT DAY WITH INTERACTION WITH THE AFOREMENTIONED
TUTT CELL AND INNER-CORE DYNAMICS (EYEWALL REPLACEMENT CYCLE) BEING
THE ONLY LIMITING FACTOR. A SLOW WEAKENING IS FORECAST AFTERWARDS AS
VWS BEGINS TO INCREASE. MODEL GUIDANCE IS IN GOOD AGREEMENT WITH
THE SLOW DOWN AND POLEWARD TURN THROUGH TAU 36. AFTER WHICH, THE
MODEL TRACKERS AND ENSEMBLE DATA INDICATE A WIDE SPREAD OF SOLUTIONS
WITH A SPREAD OF 300 NM AT TAU 72. DUE TO THIS, THERE IS HIGH
CONFIDENCE THROUGH TAU 36 AND LOW CONFIDENCE THERE AFTER.
C. STY 19W WILL CONTINUE POLEWARD ALONG THE WESTERN EDGE OF THE
STEERING RIDGE DURING THE EXTENDED FORECAST PERIOD. A TRANSIENT
RIDGE IS EXPECTED TO BUILD TO THE NORTH OF THE SYSTEM LATE IN THE
FORECAST PERIOD, INDUCING A SLIGHT WESTWARD TRACK DEFLECTION BETWEEN
TAU 96 AND TAU 120. STY 19W IS EXPECTED TO WEAKEN SLOWLY IN THE
EXTENDED PERIOD AS UPPER-LEVEL OUTFLOW BECOMES LESS FAVORABLE AND
ALONG-TRACK OCEAN HEAT CONTENT DECREASES. DYNAMIC MODEL GUIDANCE
SUPPORTS THIS FORECAST SCENARIO, BUT DEPICTIONS OF THE WESTWARD
TRACK DEVIATION AND THE EXTENT OF THE TRANSITORY RIDGE VARY. GIVEN
THIS UNCERTAINTY, THE CURRENT EXTENDED FORECAST TRACK IS POSITIONED
CLOSE TO THE MULTI-MODEL CONSENSUS WHICH HAS BEEN FAIRLY STABLE OVER
THE PAST 24 HOURS GIVEN THE WIDE RANGE OF SOLUTIONS. OVERALL, THERE
IS LOW CONFIDENCE IN THE FORECAST TRACK.//
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WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 19W (VONGFONG) WARNING
NR 24//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUPER TYPHOON (STY) 19W (VONGFONG), LOCATED APPROXIMATELY 510 NM
SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A FAIRLY SYMMETRIC ANNULUS OF DEEP CONVECTION
SURROUNDING A ROUND 23-NM EYE. A 081234Z AMSU-B IMAGE INDICATES DEEP
CONVECTIVE BANDING WRAPPING INTO THE SYSTEM. BASED ON THE ROUND EYE,
THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION AND RECENT MOTION.
THE INITIAL INTENSITY IS ASSESSED AT 145 KNOTS BASED ON DVORAK
INTENSITY ESTIMATES RANGING FROM T7.0 TO T7.5 (140 TO 155 KNOTS).
UPPER-LEVEL ANALYSIS CONTINUES TO INDICATE EXCELLENT RADIAL OUTFLOW,
ENHANCED BY A TUTT CELL TO THE EAST. STY 19W IS TRACKING ALONG THE
SOUTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE (STR). THE 08/00Z 500MB
ANALYSIS DEPICTS A BREAK IN THE STR OVER OKINAWA WITH ZONAL WESTERLY
MIDLATITUDE FLOW POLEWARD OF THE STR.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. STY 19W IS FORECAST TO TURN INCREASINGLY POLEWARD WITHIN THE
NEXT 12 HOURS AS IT ROUNDS THE SOUTHWEST PERIPHERY OF THE STR
AND TRACKS ALONG THE WESTERN PERIPHERY OF THE STR TOWARD THE
AFOREMENTIONED WEAKNESS POSITIONED NEAR OKINAWA. AFTER TAU 24,
UNCERTAINTY INCREASES DUE TO SIGNIFICANT MODEL DIFFERENCES IN THE
STRENGTH OF A MIDLATITUDE SHORTWAVE TROUGH FORECAST TO DIG OVER
WESTERN JAPAN AFTER TAU 36. THE JGSM, JENS AND ECMWF TRACKERS
INDICATE A MORE NORTH-NORTHEASTWARD TRACK THROUGH TAU 72, AFFECTED
MORE BY THE TROUGH, WHILE GFS, HWRF AND COAMPS-TC INDICATE A MORE
NORTH-NORTHWESTWARD TRACK TOWARD OKINAWA THAT REFLECTS NO
INTERACTION WITH THE TROUGH. THE REMAINDER OF THE GUIDANCE INDICATES
A GENERALLY NORTHWARD TRACK THROUGH TAU 72. ENSEMBLE GUIDANCE ALSO
INDICATES UNCERTAINTY THROUGH THIS PERIOD, REFLECTING THE COMPLEX
STEERING ENVIRONMENT AND VARYING DEGREES OF MIDLATITUDE TROUGH
INTERACTION. THE JTWC FORECAST TRACK REMAINS CONSISTENT WITH
PREVIOUS FORECASTS AND IS POSITIONED CLOSE TO THE MULTI-MODEL
CONSENSUS. STY 19W IS FORECAST TO MAINTAIN STY STRENGTH THROUGH TAU
36 BUT IS FORECAST TO GRADUALLY WEAKEN THROUGH TAU 72.
C. IN THE EXTENDED PERIOD, HIGH UNCERTAINTY REMAINS AS A
MIDLATITUDE SHORTWAVE RIDGE PROPAGATES NORTH OF THE SYSTEM AND RE-
BUILDS THE STR TO VARYING DEGREES. MODEL SOLUTIONS SHOW A WIDE
SPREAD OF SOLUTIONS IN A GENERALLY NORTH-NORTHWESTWARD ORIENTATION.
NEAR TAU 96, STY 19W IS FORECAST TO RE-CURVE NORTHEASTWARD AS IT
BEGINS TO INTERACT WITH THE MIDLATITUDE WESTERLIES AND BEGIN EXTRA-
TROPICAL TRANSITION. INCREASING VERTICAL WIND SHEAR NORTH OF 28N
LATITUDE WILL SERVE TO WEAKEN THE SYSTEM. OVERALL, THERE IS LOW
CONFIDENCE IN THE FORECAST TRACK DUE TO THE LARGE MODEL SPREAD.//
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